This invention relates generally to dynamic memory cells, and more particularly, to an improved one device memory cell wherein information is stored as a charge on a capacitive node and read by a reading device such as a field effect transistor (FET) being selectively switched on for reading the presence or absence of the charge at the capacitive node.
In the prior art, a one device dynamic memory cell with a capacitive node is connected through the cell device to a bit line which is charged to a very precise voltage. The bit line, in turn, is connected to a differential sense amplifier which, when the cell device is switched on will sense the presence or absence of a charge at the capacitive node. When the presence of a full charge is sensed, the voltage in the bit line maintains the charge at the capacitive node at essentially its full charge level thus causing the cell charge to be rewritten essentially as it is being read.
However, if a low charge is read at the capacitive node when the cell device is turned on, the voltage on this bit line will charge the capacitive node to essentially the full charge. Hence, to rewrite the low charge, the capacitive node has to be discharged.
According to the prior art technique, the discharging is accomplished by lowering the voltage in the bit line and turning on the cell device to allow the capacitive node to discharge. However, this has the serious disadvantage of significantly extending the cycle time, since a delay is encountered in bringing the bit line to a low voltage and then raising the bit line voltage to the high voltage.